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GM300 repeater build

Posted: Fri May 08, 2009 11:54 am
by n3qam
I am building a repeater with 2 gm300's for GMRS. Currently i have a RA-ID1 controller found on ebay. I am upgrading to a cat200B for the remote functions etc etc.

These are 40 watt uhf radios and programmed in rss for generic repeater mode. I currently have the transmit radio set for 25 watts , forced air on the heat sinks. I just do not trust using the on board PA. I have a UHF convertercom brick , but due to potential spurs , i do not want to turn the radio down via software.
Ive been reading around about pulling the PA deck off and cabling directly from the exciter port to the input of the external deck. This will make for an easier upgrade for a 100% duty cycle amp later down the road.

My question with removing the on board PA is , Will i have problems with the the thermistor kicking back the output at that stage? Should i just leave the deck on and keep everything hooked up MINUS the TX and have that exit out of the cover and hit my amp that way ?

Re: GM300 repeater build

Posted: Sat May 09, 2009 7:58 am
by psapengineer
Unlike Ham Radio, GMRS requires FCC type acceptance and by modifying the radio's PA you're likely voiding the type acceptance. I'm sorry I don't know the answer to your real question, I would have answered it if I did; I felt compelled to jump in and highlight the FCC issue. Best Regards, Bob

Re: GM300 repeater build

Posted: Sun May 10, 2009 6:50 am
by Doug
I think if you check out this site you may find the information you seek

http://www.repeater-builder.com/maxtrac ... index.html

Doug

Re: GM300 repeater build

Posted: Mon May 11, 2009 11:34 am
by chartofmaryland
What is the gain and loss of your antenna system?

This will tell a lot about your ability to change the PA configuration

CoM

Re: GM300 repeater build

Posted: Mon May 11, 2009 11:40 am
by n3qam
It is a db products 4 bay uhf . For the time being , it is going to be fed with about 50 feet of lmr 400 ( to be upgraded upon completion of setup and test phases) . It also has a cellwave or phelps dodge mobile duplexer , that at some point will be replaced for a better set of cans


This is the baby test machine . If we can get this done and working , it will be replaced by a ge master II we have awaiting re-tune.